They would buy from the shops because it's gonna be good weed vs taking a risk or being told that next weeks will be better. It will always be grade A at the shops
You don't need the best, IMO I knew punks that grew weed up here in cold Michigan during the summer, first generation plants and by the fall it was OK weed--no lights, not the best seeds to start with.
Some folks will buy in stores and pay the tax but not all and don't you think tobacco and alcohol sales will drop off--end result is less taxes collect, IMO